Final answer:
The number of possible gametes is found with the formula 2^n, where n is the heterozygous gene pairs. Phenotypes are determined through Punnett squares or allele combinations. The Hardy-Weinberg equation is used in population genetics to predict genotype frequencies.
Step-by-step explanation:
The number of possible gametes can be found using the formula 2^n, where n represents the number of heterozygous gene pairs. The number of possible phenotypes is generally determined through the Punnett square or by calculating the distinct combinations of alleles involved.
For example, assuming a dihybrid cross (AaBb × AaBb), where both parents are heterozygous for two genes, the number of possible gametes each can produce is 2^2=4. Phenotypic ratios can be seen in a 9:3:3:1 distribution from the resulting 16 combinations of gametes, displaying different phenotypes based on the interactions of the alleles. In a monohybrid cross, such as Aa × Aa, the phenotypic ratio would be the classic 3:1, indicating three dominant to one recessive phenotype among offspring.
In population genetics, the Hardy-Weinberg equation, p^2 + 2pq + q^2 = 1, where p is the frequency of the dominant allele and q is the frequency of the recessive allele, can predict genotype frequencies within a population assuming no evolution is occurring. When considering complex crosses, such as tetrahybrid crosses, you use the sum and product rules to calculate genotypic proportions and thus infer phenotypic proportions.